Process for the production in continuous or semi-continuous of phenol/acetone from cumene, via cumene hydroperoxide (CHP), which comprises: a. producing CHP in an air-lift reactor in which at least the upper and/or lower part of the downcomer has a flaring; b. cleaving the cumene hydroperoxide by means of acid treatment in a loop reactor comprising two heat exchangers connected in series and wherein the feedings of CHP and fresh acetone are in pairs and each pair is positioned up-stream of each exchanger.